The overall goal of this application is to build the resources to investigate the transcriptome of African trypanosomes derived from the tsetse midgut in order to prepare for future studies aimed at revealing the functional and regulatory interplay of the insect vector-trypanosome interactions. The diseases caused by trypanosomes continue to devastate humans and animals in SubSaharan Africa, with no vaccine in sight and with no efficient and affordable drugs in the pipeline. The parasite relies on a single vector, the tsetse fly, for its transmission. The recently developed paratransgenic technology in tsetse allows for the synthesis of foreign gene products in the tsetse commensal flora in the midgut environment, where they can interact with trypanosomes. The expression of products in the symbionts, which could interfere specifically with the differentiation or establishment of parasites in the midgut, would increase the efficacy of this strategy and provide a novel tool for disease control. Although the trypanosome biology in the mammalian host has been extensively studied and its genome sequence is near completion, there are few investigations on the molecular aspects of parasite biology in the tsetse vector. Much of our knowledge on the insect-stage parasite biology is based on parasite cultures maintained in vitro. The goal of this application is to identify parasite genes that have the potential to play a role in the differentiation and/or establishment processes in the midgut. Specifically, the applicant plans to obtain a quantitative measurement of gene expression levels from midgut-derived trypanosome cells using Serial Analysis of Gene Expression (SAGE) and to investigate the functional significance of selected loci during the process of differentiation in the tsetse fly. [unreadable] [unreadable] [unreadable]